(No copywrite on Tight Space by the way, Days of Wonder, feel free to make use of it)

I think that this is the next logical direction for Days of Wonder to take the series. Two entries in the Fantasy genre is plenty, especially if they keep making mini-expansions to keep the game fresh. But the next big step is always Sci-Fi.

It wouldn't even be that hard to produce. They have the mechanics already, it would just be a matter of re-painting it, and switching up the powers that are special and racial like they did with SWU. Then throw in a few new rules to go with the theme, keep the places and relics, but obviously repaint them too... Throw in some new ideas for races and powers to mix it up a bit more... But the main thing is that they have the base game, so most of the balancing and finicky work in game development is already done.

One thing I can see them doing to fit the feel of Sci-Fi better is going more generic with the race names. Pointy-eared Alien, Squid Face, Grey Ones...

One new dynamic that they could bring in is the idea of empty space. Kinda like sea in SW, or even more like the river in SWU. It would then take tokens to travel from planet to planet. Maybe have 4-6 regions per planet? Asteroids? Or give each player a limited number of space ship tokens as their only means of interplanetary travel, so that they have to decide which few directions to expand their empire.

Planet types: Desert, Ice, Water, Lava, Earth-like, City

Chris Smith over at Boardgame Geek made this mock up that shows how very cool this could be.

I was thinking of something along similar yet different lines. Something like Small Universe or Small Galaxy. To be played on a board one a galaxy (or maybe multiple ones for the larger boards) divided up. Some new elements could be Wormhole regions (you can travel between matched wormhole regions, but maybe attacking an occupied region on the other side of the wormhole comes with a -1 penalty). And you could have abilities/powers like FTL that lets you jump to further regions rather than just attacking adjacent ones.

And maybe a Realms-like version where each tile has a planetary system, or with smaller tiles being quasars or whatnot.

As you mentioned, all sorts of races and powers can be mined from scifi.

For the last year, I've been trying to develop two Underground-style stand-alone expansions. One of those (I called it SW Galaxy) draws from sci-fi elements in the same manner as is being discussed here. There is a lot of potential with science fiction races and powers to be had.

The other version I was trying to develop (SW Oceans) was more along the game's traditional lines of fantasy, but underwater. There's no shortage of race/power ideas here either.

What's been stumping me is trying to introduce a unique gameplay mechanic for each version (the way Underground did with relics/places. I wanted the games to feel different in more ways than just the overlying theme.

My other difficulty was trying to maintain comparability with SW and SWU. I concede other games wouldn't have to be compatible, but it would be so much better if they were.

Granted, I haven't played U, but I've read the rules quite a bit, especially the bit about using U races/abilities on the base game.

To call it "compatible" is a bit of a stretch in my opinion. You have to throw out a lot of stuff related to Relics, Places, Terrain, etc. The same is true if you try to bring base Powers and Races underground. Humans are NOT invited unless they want to try to farm. And you're going to have to do more mental conversion (Muddy = Swamp).

So I wouldn't worry about it as much. I'd say let it be its own thing. As I mentioned above, I think it could have it's own Realms-type variant and that'd be compatibility enough.

And I think there are plenty of U-like spins you can put on it to make it it's own. Like I mentioned about the wormhole (or perhaps a gate network?) You could have Alien Artifacts that are powerful technologies left over by ancient civilizations (like Relics). You could have all sorts of Places like Antimatter Factory, Monopole Mines, Dyson Sphere, Galactic Archive, and so on.